Contrast that with sales of Mafia III, a game that was initially 2K's fastest-selling launch game. First releasing in November, Mafia III sold 4.5 million copies in its first week, but 2K parent company Take-Two announced lifetime sales have now reached 5 million, meaning only half a million copies have been sold since the first week.

During its quarterly call with investors, Take-Two Interactive called Grand Theft Auto V's sales "better than expected," helping Take-Two's net revenue growth of 15% over the same period last year.

Grand Theft Auto V originally launched on PS3 and Xbox 360, with a PC version coming later. The game then made the jump to PS4 and Xbox One, and owners of the older versions could move their saves from the earlier versions to the more modern consoles. The Grand Theft Auto V transfer program ends next month, so if you've been dragging your feet, time is running out.

UPDATE:This story was updated to add Mafia III sales information.

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